1. Field of the Invention
The present invention relates to a digital camera.
2. Description of Related Art
As a method of autofocus (AF) of digital cameras, a contrast detection method is heretofore known. In the contrast detection method, image signals are obtained by imaging a subject with an image sensor such as a CCD, a component of a predetermined spatial frequency band is extracted from the signals contained within a predetermined AF area within an image and a focus evaluation value is calculated by integrating its absolute value. The focus evaluation value is a value that corresponds to the contrast in the focal point detection area, and the value increases as the contrast increases. Japanese Patent Application No. 2003-315665 discloses an art that, based on characteristic that the contrast of an image becomes higher as a focus lens assumes a position closer to a focus position, the lens position at which the focus evaluation value peaks (hereafter referred to as the peak position) is determined, the peak position is judged to be the focus position, and the focus lens is driven to this focus position.
However, for detecting the peak position of the contrast, which is the focus position, the focus evaluation values are calculated at predetermined intervals, moving the focus lens along an optical axis, the focus evaluation values of those points are analyzed, and the peak position is detected. Therefore, there has been a problem that focus matching takes time and a moving subject can not be focused on.